The invention relates generally to needle bearing cups, and more particularly to double drawn needle bearing cups having a shell formed from an outer cup and an inner cup.
FIG. 1 (PRIOR ART) is a cross sectional view of a conventional drawn needle bearing cup. Conventional needle bearing cup 10 includes a cylindrical shell 12 which is drawn from a piece of flat stock. Inner surface 14 of needle bearing cup 10 forms a bearing raceway for a plurality of rolling elements (not shown). The top portion of needle bearing cup 10 has a thinner cross section and is conventionally referred to as a lip 16. Needle bearing cup 10 houses a number of internal components such as the aforementioned rolling elements. Additional internal components may include a retainer cage to hold and guide the rolling elements, one or more seals, and less commonly, washers or rings for more specialized purposes.
FIG. 2 (PRIOR ART) illustrates conventional needle bearing cup 10 having a number of internal components 18 installed within cylindrical shell 12. Lip 16 is then bent over during final assembly to retain the internal components. In order for lip 16 to be formed and maintain the required ductility during final assembly, lip 16 is not heat treated to the same extent as required for bearing raceway surface 14. Thus, a special heat treat process is required which prevents lip 16 from being fully hardened when bearing cup 10 is heat treated. In the alternative, an additional temper or anneal process is required to soften lip 16 prior to forming in the bent over position during final assembly.
The foregoing illustrates limitations known to exist in present devices and methods. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.
In one aspect of the invention, this is accomplished by providing a bearing cup including an inner bearing cup having an inner surface which forms a bearing raceway. The inner bearing cup has a corresponding length. An outer bearing cup is disposed about and continuous with the periphery of the inner bearing cup and has a corresponding length which is longer than the length of the inner bearing cup to form a lip. The lip of the outer bearing cup may be formed to retain rolling elements within the bearing cup.
In another aspect of the invention, the limitations of the prior art are overcome by providing a method of forming a bearing cup having an inner bearing cup and an outer bearing cup. The method includes cutting first and second sheet metal sections into first and second sheet metal blanks. The first and second sheet metal blanks are then drawn to form a double walled bearing cup including an inner bearing cup corresponding to the first sheet metal blank and an outer bearing cup corresponding to the second sheet metal blank. A lip is formed from the outer bearing cup and extends beyond a top portion of the inner bearing cup. Roller elements are then installed within the inner bearing cup and the lip is bent over to retain the rolling elements within the inner bearing cup.
The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing figures.